Schemas, Patterns, Frames and Knowledge in Systems Development

1. Schemas, Patterns, Frames and Knowledgein Systems Development Lecture 10

2. Topics • Schemas, Patterns and Frames in computing and psychology • A problem – The Police Identity Parade • Multiple levels of Frames • Repository • Simulation • Decision support • Matching problems

3. Schema in Database Development descriptive What is a route? service schema Domain of Discourse Use prescriptive A route is a …

4. Database Schema in Use • Schema has a fixed structure with a set of place holders to allow variation: • A slot for the single destination of all buses on the route • So a route can’t have multiple destinations • But the last 70 goes to Muller Road Depot, not Centre • So this will have to be a different route • Or alter schema to allow over-ride destination in departure • A Schema structures our perception of the world • We change the schema when the fit is poor

5. Minsky’s Frames • Marvin Minsky is one of the fathers of artificial intelligence • “When one encounters a new situation (or makes a substantial change in one's view of the present problem) one selects from memory a structure called a Frame. This is a remembered framework to be adapted to fit reality by changing details as necessary” • “A frame is a data-structure for representing a stereotyped situation, like being in a certain kind of living room, or going to a child's birthday party. Attached to each frame are several kinds of information. Some of this information is about how to use the frame. Some is about what one can expect to happen next. Some is about what to do if these expectations are not confirmed.” • “Thinking always begins with suggestive but imperfect plans and images; these are progressively replaced by better–but usually still imperfect–ideas.” • Marvin Minsky, A Framework for Representing Knowledge, MIT-AI Laboratory Memo 306, June, 1974

6. Gestalt psychology • ‘Gestalt’ – form; pattern; shape; organised whole or unit • notion of pre-existing schemata, or organisational frameworks for structuring information, as opposed to perception built up from visual stimulus alone. • In the case of visual perception, a schemata provides a framework within which external stimuli are sensible. [A frog’s visual and motor system is pre-programmed for fly-recognition]

7. Design Studies • Cognitive psychologists observe that for an experienced analyst designing a familiar object in a familiar domain, the overall task could be characterised as being dominated by the retrieval of previously-stored knowledge (Adelson and Soloway). • Research by Curtis et al has shown the importance of domain knowledge in design, where domain knowledge entails understanding of the problems which occur in a specific application field and the tried and tested (and the failed) solutions. • Brown and Chandrasekaran identify the strategy of 'Design by Critiquing and Modifying Almost Correct Designs' as one of four main design processes (decomposition, design plans, and constraint solving are the others).

8. Pre-structuring • Hillier, Musgrove and O'Sullivan suggest that [building] design is essentially a matter of prestructuring problems based on the designer's knowledge : • of solution types • of the 'latencies of the instrumental set' (the raw materials + time) in relation to solution types • of informal 'codes' which relate problems to solution types • “it is not a matter of whether the problem is pre-structured but how it is pre-structured, and whether the designer is prepared to make this prestructuring the object of his critical attention” • Hillier Musgrove and O’Sullivan Knowledge and Design 1972

9. Patterns • Christopher Alexander and colleagues wrote an influential collection of 253 ‘patterns’ for living – good solutions to recurring problems in architecture. • Language intended to provide a basis for community architecture • Gamma et al picked up this work and applied it to the emerging area of Object-oriented Programming. • Provides a language for developers to use within a project • ‘We need the Observer pattern here’ • Pattern conferences develop a rich array of patterns encapsulating the experience of developers in many software and organisational contexts.

10. Language Patterns • Web development requires knowledge of many languages: SQL, PHP, JavaScript, CSS, XHTML ++ • Formal languages have common problems to solve, but solve them in different ways • e.g. separating natural language (comments) form the formal language • Sequence, iteration and selection • Strings • Arrays • My Language patterns project is attempting to create a reference book of language patterns and their solution in a range of languages

11. Jackson’s Problem Frames • “An inability to discuss problems explicitly has been one of the most glaring deficiencies of software practice and theory. Again and again writers on development methods claim to offer an analysis of a problem when in fact they offer only an outline of the solution, leaving the problem unexplored and unexplained” • Jackson adopts a more formal, analytic approach to problem analysis and has identified a small number of Problem Frames. [more in a later lecture]

12. Some Frames in Information Systems Resource Management Case handling Information Display Decision Support WorkPiece Required Behaviour Classifying Commanded Behaviour Matching (Jackson’s Problem Frames) Transformation Repository

13. Problem: Police Identity Parade (PIP) • Read overview • In summary: • Police station has to arrange an identity parade in which a suspect is placed alongside ‘similar’ persons and a witness asked to identify a person seen at the crime.

14. What Kind of System is it? • a repository of data • a model of a Domain of Discourse • a decision support system • For police officers selecting volunteers • For the witness identifying persons at the scene of crime • a co-ordinator of human activity • a tool for the construction of an artefact • a learning system • ..... • Real systems have aspects of several kinds but it helps to focus of each viewpoint in turn, then integrate them – divide and rule

15. Repository Frame (Data Store) • Common to view an information system as a simple repository of data. • Data is collected, stored, kept safe from falling into the wrong hands, from being lost. • Data can be extracted, reorganised, removed if no longer relevant • Data should only be accepted if it conforms to rules for good data -‘integrity rules’ • Also called CRUD (Create, Retrieve, Update, Destroy) • Repository may be computer based or in some other form – paper, brain, organization

16. Repository Frame in PIP • In the problem, we need to be able to • store data about suspects and volunteers • readily retrieve data when required • keep the data secure from loss, or access by the wrong people • Metaphor : SYSTEM IS A BANK

17. Transformation Frame (Process) • An input in one format or medium is converted into an output in another format or medium: • Converting from the temperature of a room into a 4 bit digital value • Converting from XML to HTML • Converting from text to speech • Converting from printed matter to text (OCR) • Subsidiary Processes: • Parsing –understanding the structure of the input • Filtering out irrelevant parts of the input • Merging multiple inputs • Connecting the output of one transformation to the input of another • METAPHOR : system is a PRODUCTION LINE

18. Transformations in PIP • Volunteer interviewed and physical characteristics recorded • Facial image captured and transformed to an image on a screen • Typed statements OCRed

19. Information Display(Map) Frame • System contains a model of the ‘domain of discourse’ . This model is used to present re-organised data about the domain of discourse. • Issues: • How much of the real world to model, in what detail to support needs of users, now and in the future? • How to ensure that the model and the real world stay closely in synchrony - that changes to the real world (a volunteer moves house) are reflected in the model (address field updated) quickly and accurately • How best to represent the model for specific purposes and audiences • Metaphor: SYSTEM IS A MAP

20. Information Display in PIP • How is a suspect to be represented in the system for the purposes of the PIP? • How is a volunteer to be represented? • How do we know when a volunteer changes in some relevant way? • Removes beard • Moves • Who should be able to view the suspect’s details?

21. Frame relations • Information Display Frame uses: • Repository for persistent storage of model • Transformation • In mapping real world phenomena into symbols in the repository • In representing symbols in the repository to observable phenomena

22. Other IS Frames to be explored • Business Level • Resource Management • Case handling • Decision Support • Business Transaction • … • Generic Frames • Matching • Classifying • …

23. Resource Managment Frame • Allocation of scarce resources, such as • seats on flights • rooms for lectures • beds for patients • volunteers to identity parades • Problem is to maximise utilisation of resources whilst minimising delay and inconvenience to parties • Common Issues • Granularity of resource units • Handling time • Modelling and visualising allocations • Cancellation policy • Over-booking policy • Allocation policy - priorities, up-grading … • A common sub-problem is to match a client’s needs to available resources

24. Matching situations • From the easy to the very hard: • A word to a dictionary of valid words • A poorly typed word to a dictionary of valid words • T9 speedtexting • A customer on the phone to bank accounts • De-duping mailing lists • CD DB - CD recognition • Shazam – sound sample matching • COTS selection • IS development approach selection

25. Matching Frame • Matching typically involve: • A Requirement and multiple Resources:| • the sample of music / suspect - Requirement • the database of tracks /volunteers – Resources • ‘adequate’ representations of both • A definition of how to measure how well matched a Requirement is to a Resource • A process to select the best match: • Automated < > human • One-off <> iterative

26. Anagrams • Find an anagram for an English word • ORCHESTRA • Matching function: • Break word into letters and sort the letters • ACEHORRST • Match with a dictionary in which all words have a sorted letters field • CARTHORSE • HORSECART

27. Shazam - 2580 • Shazam is a mobile phone application • It can recognise 1.7 million tracks from a 30 sec sample – new tracks added at 5,000 a week • The track details are texted back within about 30secs • It costs 50p + 9p call charge (surcharge only if successful) • Your personal page shows the tracks you have tagged • www.shazam.com

28. CD DB • Database of 2.5 million CD’s, track details and supporting matter run by gracenote (www.gracenote.com) • Used by media players to obtain track info • Player sends signature of CD [sequence of track lengths in 1/4sec] to match against the database (via HTTP) • Application searches DB for best match and returns track info to media player. • Matching algorithm described in US Patent 6,061,680

29. De-duping A catalogue from O’Reilly C Wallace West England University Coldharbour Lane Frenchay Bristol BS16 1QY Ms C Wallace Univ. of the West of England Frenchay Campus Coldharbour Lane Bristol BS16 1QY One person or two? Mailing lists are reported with 25 – 40% duplicates.

30. Commercial Of the Shelf Software (COTS) • Software exists for most business needs: • payroll • order processing • general ledger • human resources • e-commerce • e.g. SAP, SAGE .. • Analysts need to match business needs to COTS capability, and customise generic software for local business rules.

31. Police ID parade • Currently: • Suspect matched to Volunteers visually by officer • Information System • Suspect and Volunteers modelled in database • System provides list of matching volunteers

32. Frame Approach to Development • Rough description of Problem • Select suitable Frame(s) to fit Problem • A well-fitting Frame provides: • standard terminology • checklist of issues which need to be addressed, questions which need to be asked • index of solutions to commonly occurring sub-problems • Frame allows us to draw upon relevant prior knowledge of this problem type • Identifying appropriate Frames is a Matching Problem!

33. Tutorial Questions • PIP • Identify aspects of the Police Identity Parade problem which map into these Frames: • Repository • Information Display • Resource Management • Matching • What analysis questions do these frames suggest? • What is left out? • Matching • Suggest 3 other applications whose core frame is ‘matching’